1. Field of the Invention
The present invention relates to a solenoid-operated valve for use in internal combustion engines which can be opened and closed under electromagnetic forces generated by solenoids or electromagnets.
2. Description of the Related Art
There have heretofore been known solenoid-operated valves for opening and closing exhaust passages in the cylinders of internal combustion engines under electromagnetic forces. The known solenoid-operated valves have a pair of solenoids or electromagnets confronting and spaced from each other, and a disk-shaped movable plate of magnetic metal disposed movably between the solenoids. The disk-shaped movable plate is fixed to the upper end of a valve stem which has a valve body on its lower end. The valve stem is slidably supported by and extends through an upper wall of an exhaust passage from an engine cylinder, with the valve body being positioned to selectively open and close the exhaust passage.
The disk-shaped movable plate is normally urged downwardly to open the exhaust passage by a spring positioned above the disk-shaped movable plate, and is also normally urged upwardly via the valve stem to close the exhaust passage by another spring positioned beneath the disk-shaped movable plate. The springs have equal resilient forces exerted to bias the disk-shaped movable plate in mutually confronting directions for thereby holding the disk-shaped movable plate intermediate between the solenoids.
When the exhaust stroke of the engine cylinder is completed, the upper solenoid is energized to magnetically attract the disk-shaped movable plate upwardly, so that the sum of the upward magnetic attractive force of the upper solenoid and the repelling force of the lower spring overcomes the biasing force of the upper spring thereby to displace the valve stem upwardly to cause the valve body to close the exhaust passage. When the exhaust stroke of the engine cylinder is started, the lower solenoid is energized to magnetically attract the disk-shaped movable plate downwardly, so that the sum of the downward magnetic attractive force of the lower solenoid and the biasing force of the upper spring overcomes the repelling force of the lower spring thereby to displace the valve stem downwardly to cause the valve body to open the exhaust passage.
At the start of the exhaust stroke of the engine cylinder, the internal pressure of the engine cylinder is relatively high and acts on the valve body in a direction to close the exhaust passage. Therefore, the valve body suffers a delay in its movement to open the exhaust passage, resulting in a failure to meet demands for higher rotational speeds and output power of the internal combustion engine.
One solution would be to increase the magnetic forces of the lower solenoid by supplying an increased current to the lower solenoid for thereby attract the diskshaped movable plate downwardly at an increased speed. However, the increased current supplied to the lower solenoid would be disadvantageous in that the solenoid-operated valve needs to have an increased power requirement.